280 MOEPHOLOGY AND EVOLUTION
of the fissure is present, and is frequently bifid at its posterior extremity. Its inclination varies, and in some cases it should really be called a posterior ascending limb. The anterior limbs are not properly constituted as in ilan, and a part of the insula is exposed to view. The parallel sulcus may hook round the upper end of the Svlvian fissure.
The ealcarine fissure is well marked in the Apes and in Man. It is really a complex of true calcarine and retro-calcarine sulci in the Apes, but these component sulci remain separate in Man. It produces the elevation in the lateral ventricle which is known as the calcar avis. The calcarine sulcus is not connected to the calloso-marginal sulcus ^intercalary sulcus of Elliot Smith) as it is In many lower animals. It is embraced by the diverging limbs of the Y-shaped lateral occipital sulcus.
The hippocampal fissure is constant in the Apes.
The Apes have a large " simian sulcus," or " AfFenspalte," which sweeps across the hemisphere. It may cross the margin of the great longitudinal fissure. It may be concurrent with the transverse occipital sulcus. It lies behind the parieto-occipital sulcus, and may pass into it. The transverse occipital sulcus receives the caudal extremity of the intraparietal sulcus. In Man the small sulcus lunatus corresponds to the Affenspalte.
The intraparietal sulcus ib really a complex of sulci, and the system includes one or both postcentral sulci.
On the infero-lateral aspect of the occipital lobe there are to be found inferior occipital and occipito-temporal sulci; and the latter may increase in size at